Most effective way for hitTesting

Alrighty, I’m making a missile command game, you can see the test version here.

I was wondering what would be the easiest/most effective way to hitTest the duplicated missiles with the duplicated rockets. Right now I’m using a for loop, the only problem with that is when there are multiple rockets on the screen using the for loop to hitTest the missiles it becomes very laggy. Any better ways to hitTest you think?